The Democrats will ask two state agencies to look into the propriety of Parliament president Somsak Kiatsuranont's nine-day "study trip" to Europe.
The junket with 39 aides, media members and academics said to be mainly sympathetic to the governing Pheu Thai party is costing taxpayers 7 million baht.
The high point of the trip for many of the participants, apparently, will be Sunday's Premier League match between Liverpool and Manchester United, though Mr Somsak has said he would pay for that outing.
Sathit Pitutacha, a member of the Democrat Party's executive board, said on Saturday that he would file petitions with the Office of the Ombudsman and the National Anti-Corruption Commission (NACC) asking them to investigate Mr Somsak.
This article is older than 60 days, which we reserve for our premium members only.You can subscribe to our premium member subscription, here.